So I'm currently working on a fan project to redesign Superman's home planet of Krypton.

This new Krypton is 1.6x the size of Earth and orbits the red dwarf star known to us as LHS-2520, 27.1 lightyears from Earth.

In an attempt to give a lot of geographical detail to Krypton, I considered making the planet's core predominantly comprised of Krypton which is as an element is not nearly as dense as the elements that make up Earth's Core and it is fairly rare. It would be impossible for a planet to form from Krypton naturally but if it could, what would the results be.

Could a planet function with this type of core and what features would it have?

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    $\begingroup$ The reason that the Earth's core is denser than the mantle, is that dense stuff sinks in less dense stuff. There's no mechanism by which a planet could form a Krypton core, unless the mantle were even less dense than it. $\endgroup$ Commented Aug 11, 2019 at 21:07
  • 4
    $\begingroup$ Note that the writers of Superman have never really suggested that "Kryptonite" is made primarily of the element Krypton. $\endgroup$
    – Hypnosifl
    Commented Aug 12, 2019 at 0:39
  • $\begingroup$ You do not need kryptoniaan core. The superpowers of Superman originates from our Sun "radiation" by canon, if I remember it right. It our Sun is special, not Superman. Krypton just reduces and neglects this "radiation" and is just a "common" mineral far from Sun. $\endgroup$
    – ksbes
    Commented Aug 12, 2019 at 9:12

1 Answer 1


Your planet will either be incredibly cold, or have no heavy elements.

Krypton is a fairly light noble gas, it boils at 119K, and it's fairly rare. Naturally, such an element would never form the core of a planet. Even for planets where krypton occurs as a solid, heavier, denser materials will sink and form the core of the planet, especially when the planet is young and hot.

However, it would be possible to form a planet with a krypton core artificially, in one of two ways.

First, if your planet is incredibly cold, you could conceivably build a core of solid krypton, and then slowly add more materials to build up a planet on top of your core. If your planet is cold enough that nothing moves around, you'll end up with a krypton-cored planet. Your planet will be cold and inert, with no plate tectonics, earthquakes, or volcanoes. It will be far from its star. Superman might be able to live, there, but it wouldn't be much fun.

Second, you could have a planet where krypton is the densest material. Natural processes that can form Krypton can also form heavier elements, so this would never happen naturally. However, if your super advanced aliens were to strip all of the krypton out of a planet like Jupiter, and throw in some lighter elements to round out the planet, you could conceivably create a planet where krypton was the densest material available, and hence sank and formed the core. This would only happen if the planet were either gaseous, with the rest of the planet made of gasses less dense than krypton, or else if the planet was cold enough that the krypton solidified.

All of these planets could only be formed artificially, and none would support life.


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